1. Field of Invention
The present invention relates to a contact pad, and a thin film transistor substrate and a liquid crystal display panel having the same. More particularly, the present invention relates to a contact pad formed as a structure for increasing corrosion resistance and durability, and a thin film transistor substrate and a liquid crystal display panel having the contact pad.
2. Description of the Prior Art
A liquid crystal display (LCD) is advantageous for being lightweight, and can be used in both small and large screen applications in comparison to a conventional cathode ray tube (CRT), so that LCD research and development are actively pursued. The LCD is used in various display applications, e.g., desktop computer monitors, large displays for home video and projection and small displays for mobile devices. The application range for LCDs is rapidly expanding. To display an image on an LCD panel, an LCD controls light transmissivity according to image signals applied to control switches arranged in a matrix. An LCD typically includes an LCD panel having a liquid crystal layer provided between a color filter substrate and a thin film transistor (TFT) substrate, an LCD driving integrated circuit (IC) for operating the LCD panel, a backlight unit used as a light source of the LCD, and a chassis for integrating the above components of the LCD. Contacts are provided to electrically connect the TFT substrate and the color filter substrate.
Contact pads are formed in a peripheral region of the TFT substrate for connecting to a common electrode formed on the color filter substrate, so as to provide a common voltage to both electrodes.
Since the connection is positioned between the contact pad of the TFT substrate and the common electrode of the color filter substrate, the connection is compressed by both substrates. As a result, a trace may be compressed by the common electrode of the color filter substrate, i.e., an impression, is left on the contact pad. If a contact pad is thereafter exposed to humidity, corrosion may spread, so that the entire contact pad may become corroded. Consequently, since a common voltage may no longer be uniformly applied to the common electrode of the color filter substrate, failures in the display may result.